The complex kinematics, anatomical features and load distribution on an elbow are such that surgical replacement thereof is not simple. Simple constrained and semi-constrained cemented replacements for the elbow joint have proved to be generally unsatisfactory as they do not provide sufficient range of motion and, due to the unnatrual stresses placed on the musculature, ligaments and tendons, premature loosening often within a year or two of placement frequently occurs. Loosening is usually accompanied by pain and discomfort and over a period of time distortion of the natural function of the joint may occur. The use of unconstrained resurfacing prostheses, such as those described in the aforesaid application Ser. No. 507,378 and in U.S. Pat. No. 4,242,758 issued 6 Jan. 1981 to Amis et al, appears to offer the potential, by reproduction of normal joint geometry and restoration of ligament balance, to recreate relatively normal kinematics and load bearing and to provide relief of pain. Such prostheses are now generally using the relatively recently developed porous metal coating technique so as to promote bone ingrowth, and this technique precludes the use of cements to secure the prosthesis to the bone or to compensate for cutting inaccuracies. It is now necessary to ensure accurate resection of the bone ends to within a tolerance of 1mm or better. Such accuracies are not possible using commonly available jigs or with hand held saws or other cutting tools such as router tools.